Weighing-scale.



No. 821,221. PATENTED MAY 22, 1906. J. B. 0001mm & 0, L. PLUMTRBE.

WEIGHING SCALE.

APPLICATION FILED APR. 6, 1995.

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PATENTED MAY 22, 906.

J. E. GOGHRAN & 0. L. PLUMTREB.

WEIGHING SGALB.

APPLICATION FILED APR. 6, 1905.

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UN ITEI) STATES PATENT. OFFICE.

JOSEPH E. COCHRAN AND OLIVER L. PLUMTREE, OF CHICAGO, ILLINOIS; A PLUTREE A SIGN B O AID COCHR N- WElG lNG SCALE! Specification of LettersIatent.

iratented IVIay 22, 1906.

Application filed April 6, 1905. Serial No. 254,090.

county of Cook and State of Illinois, have invented a certain new anduseful Improvement in VVeighing-Scales, of which the following is aspecification.

The objects of this invention are, first, to provide a simple yetsensitive and accurate scale in which a counterweight is employed tobalance the object to be weighed; second, to

render the scale of large capacity with the employment of a smallweight, and, third, to-

provide simple and positive means for overcoming the effect of backlashand bringing the pointer accurately to the reading-points. We accomplishthese objects by the mechanism illustrated in the accompanying drawings,in which I Figure 1 is a side elevation of the complete scale in itspreferred form, a portion of the dial and frame being broken away toexhibit the working parts of themechanism. Fig. 2 is "a plan view of thescale, partly in section, on the line 2 2, Fig. 1. Fig. 3 is afragmentary detail view showing a modification in the manner ofconnecting the segment of the weighted arm to the rack on thescale-beam. Fig. 4 is a fragmentary view showing another modification inwhich the segment on the weighted arm is geared directly to the rack onthe scale-beam, and the pinion on the pointer-shaft is also geared tosaid rack.

Similar letters refer to similar p arts throughout the several views.

Referring to the form of mechanism shown in Figs. 1 and 2, a representsthe scale-beam, Which is fulcrumed upon the post I) of the machine-frameb. Saidbeam is fulcrumed between its ends and at one end carries thescale-pan, and consequently when an object to be weighed is placed uponsaid pan the opposite end of the scale-beam tends to rise.

The rack d is secured to the scale-beam on the side of the fulcrumopposite to pan 0 and in the present construction is rigidly secured atthe extremity of the beam and is curved in such manner that its toothededge is circular and concentric with the fulcrum of the scalebeam. Thearm 6 is pivoted upon the shaft or pin b fixed in the framework 1), andhas a weight 6 attached thereto for counterbalancing the object to beweighed. It is desirable to provide means whereby said Weight may beadjusted upon the arm e, and a suitable form of adjusting means is shownin Fig.

1, where the extremity of arm e is threaded and carries an adjusting-nut6 A toothed, segment f is rigidly secured or connected to arm 6 in suchmanner that its toothed edge is.

concentric with the fixed shaft or pin N. The parts are so arranged andproportioned that segment f meshes with rack d, the point of engagementlying between the scale-beam fulcrum and the shaft 6 As a result of thisarrangement the arm e and counterweight 6 will swing toward the scale-pan during Weighing, with a resulting economy in space required for theoperation of the mechanism.

When the scale-pan is in normal or zero position with no weight thereon,arm 6 will lie pendent; but when an object is placed upon the scale-panthe arm 2 and weight e thereon will tend to be swung inward and towardhorizontal position. As is well known, the leverage or torsion of thecounterweight e upon arm e and segment f will increase as the arm 6approaches more nearly to horizontal position, and these parts willtherefore countermeans consists of a pointer g, adapted to rotate infront of the dial h. Said ointer is mounted upon the horizontal sha t i,journaled in the framework 1), and has rigidly secured thereto a pinion'i. Said pinion is rotated by means of a rack which is-pivotallyconnected to the scale-beam and is influenced to approach said pinion bymeans of the arm 9', which is rigidly secured to rack and so designed asto lie approximately horizontal. On said arm is a weight 7' which bypreference is adjustable on said arm and may be secured in properposition thereon by means of the set-screw 9' A guard or keeper 7c isfixed to the framework 1) at a point slightly behind rack j, thedistance beingsufficient to permit said rack to recede slightly frompinion i, so that the parts may intermesh loosely, but the distancebeing insufficient to permit rack from becoming disengaged from saidpinion. It is desirable that the pitch-line'of rack j be circular andconcentric With the scale-beam fulcrum.

In 0 eration an object upon the scale-pan will raise the rack (1, Whichwill in turn rotate the segmentf and swing the counterweight e up towardhorizontal position, the amount of swing depending upon the weight ofthe object in the scale-pan. The upward motion of the scale-beam willalso raise the rack j and rotate pinion 'i and pointer g an amountcorresponding to the weight of the object in the scale-pan. The teeth onrack j and pinion 1', are preferably involute, and when said rack movesu ward, especially if the movement be rapi there will be a tendency forsaid rack to be forced away from pinion 'L. A slight amount of recessionis an advantage, as the parts will. then be more loose and the frictionwill be correspondingly reduced. The pin 70, however, will preventactual disengagement of the rack from the pinion. I/Vhen the scale-beamhas risen to the position in which there is a balance, the weight 7'acting upon rack j, will influence said rack to closely approach piniont. This will cause said rack to bind the pinion somewhat tightly, thuseliminating backlash and bringing the pointer g to absolutely-correctposition. This construction of the pivoted and weight-influenced rack jis of great i-mportanoe and advantage, for it automatically permits theloosening of the rack from the pinion while the scale-beam is moving andthen automatically causes the tightening of the rack against the pinionwhen the scalebeam is brought to rest in balanced position. It will benoted that the construction is eX- tremely simple, rackj and arm jvirtually constituting a single piece and the mechanism being devoid ofsprings or other sources of inaccuracy and danger of breakage.

Referring to the form of device shown in Fig. 3, the construction ingeneral and in theory is the same as before, but of the racks d and oneis eliminated and the remaining one caused to serve the double urpose.Here the rack j is pivoted to the sea e-beam, as before, and meshes withpinion i; but the segment f instead of being driven by a separate rackis driven by the pinion 'L, acting through the agency of pinion m, whichis mounted upon the fixed shaft m and serves as an idler to obtain theproper relative movements of arm 6 and scale-beam a. chief object ofsaid idler-pinion m is to cause arm and weight e to swing inward towardthe machine when it moves from the zero or pendent position. Theadvantage of the movement of arm 6 in such direction is mechanicalmerely because it renders the ma chine more compact. The chief advantageof the form of device shown in Fig. 3 is that a single rack is made toperform the double functions of racks d and j of the form shown in Fig.1.

Referring to Fig. 4, the arrangement is analogous to the one shown inFig. 3, with the exception that the idler m is omitted and both pinion iand segment f mesh directly with rack The advantage in this lastdescribed form over the form shown in Fig. 3 is that the extra wheel m isomitted, with the consequent elimination of backlash.

What we claim as new, and desire to secure by Letters Patent, is

In a weighing-scale, the combination, with the seal ebeam andbean1support of a wei ghted arm, a toothed segment rigid with said arm,a rack rigidly secured to said scalebeam and meshing with said segment,a second rack upon said beam, a rotatable reading member and a pinionfor rotating the latter, said second rack meshing with said pinion forrotating it and the reading member.

In witness whereof we have hereunto subscribed our names in the presenceof two witnesses.

JOSEPH E. COCHRAN. OLIVER L. PLUMTREE.

Witnesses:

DWIGHT B. OHEEVER, HOWARD M. 00X.

The

